Method for forming photomask and photolithography method

ABSTRACT

A method for forming a photomask is provided. The method includes forming a light blocking layer over a transparent substrate. The method includes forming a mask layer over the light blocking layer. The mask layer covers a first portion of the light blocking layer, and the first portion is over a second portion of the transparent substrate. The method includes removing the light blocking layer, which is not covered by the mask layer. The method includes removing the mask layer. The first portion of the light blocking layer is removed during removing the mask layer. The method includes removing the second portion of the transparent substrate to form a first recess in the transparent substrate. The method includes forming a first light blocking structure in the first recess.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.62/591,835, filed on Nov. 29, 2017, the entirety of which isincorporated by reference herein.

BACKGROUND

The semiconductor integrated circuit (IC) industry has experienced rapidgrowth. Technological advances in IC materials and design have producedgenerations of ICs. Each generation has smaller and more complexcircuits than the previous generation. However, these advances haveincreased the complexity of processing and manufacturing ICs.

In the course of IC evolution, functional density (i.e., the number ofinterconnected devices per chip area) has generally increased whilegeometric size (i.e., the smallest component or line that can be createdusing a fabrication process) has decreased. This scaling-down processgenerally provides benefits by increasing production efficiency andlowering associated costs.

However, since feature sizes continue to decrease, fabrication processes(e.g. photolithography processes) continue to become more difficult toperform. Therefore, it is a challenge to form reliable semiconductordevices at smaller and smaller sizes.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It shouldbe noted that, in accordance with standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIGS. 1A-1E are cross-sectional views of various stages of a process forforming a photomask, in accordance with some embodiments.

FIGS. 1A-1 to 1E-1 are top views illustrating the photomask of FIGS.1A-1E, in accordance with some embodiments.

FIGS. 1A-2 to 1E-2 are perspective views illustrating the photomask ofFIGS. 1A-1E, in accordance with some embodiments.

FIG. 2 is a cross-sectional view of a photomask, in accordance with someembodiments.

FIG. 3 is a cross-sectional view of a photomask, in accordance with someembodiments.

FIG. 4 is a cross-sectional view of a photomask, in accordance with someembodiments.

FIG. 5 is a cross-sectional view of a photomask, in accordance with someembodiments.

FIG. 6 is a cross-sectional view of a photomask, in accordance with someembodiments.

FIG. 7A is a cross-sectional view of a photomask, in accordance withsome embodiments.

FIG. 7B is a top view illustrating the photomask of FIG. 7A, inaccordance with some embodiments.

FIGS. 8A-8C are cross-sectional views of various stages of a process forforming a photomask, in accordance with some embodiments.

FIG. 8C-1 is a top view of the photomask of FIG. 8C, in accordance withsome embodiments.

FIG. 9 is a cross-sectional view of a photomask, in accordance with someembodiments.

FIG. 10 is a cross-sectional view of a photomask, in accordance withsome embodiments.

FIG. 10A is a top view of the photomask of FIG. 10, in accordance withsome embodiments.

FIG. 10B is a top view of the photomask of FIG. 10, in accordance withsome embodiments.

FIG. 11 is a cross-sectional view of a photomask, in accordance withsome embodiments.

FIGS. 12A-12D are cross-sectional views of various stages of a processfor forming a semiconductor device structure, in accordance with someembodiments.

FIGS. 13A-13C are cross-sectional views of various stages of a processfor forming a semiconductor device structure, in accordance with someembodiments.

FIGS. 14A-14E are cross-sectional views of various stages of a processfor forming a photomask, in accordance with some embodiments.

FIG. 15 is a cross-sectional view of a photomask, in accordance withsome embodiments.

FIG. 16 is a cross-sectional view of a photomask, in accordance withsome embodiments.

FIG. 17 is a cross-sectional view of a photomask, in accordance withsome embodiments.

FIG. 18 is a cross-sectional view of a photomask, in accordance withsome embodiments.

FIG. 19 is a cross-sectional view of a photomask, in accordance withsome embodiments.

FIGS. 20A-20C are cross-sectional views of various stages of a processfor forming a photomask, in accordance with some embodiments.

FIG. 21 is a cross-sectional view of a photomask, in accordance withsome embodiments.

FIG. 22 is a cross-sectional view of a photomask, in accordance withsome embodiments.

FIG. 22A is a top view of the photomask of FIG. 22, in accordance withsome embodiments.

FIG. 22B is a top view of the photomask of FIG. 22, in accordance withsome embodiments.

FIG. 22C is a cross-sectional views illustrating the photomask along asectional line II-II′ in FIG. 22B, in accordance with some embodiments.

FIG. 23 is a cross-sectional view of a photomask, in accordance withsome embodiments.

FIG. 24 is a cross-sectional view of a process for forming asemiconductor device structure, in accordance with some embodiments.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the subject matterprovided. Specific examples of components and arrangements are describedbelow to simplify the present disclosure. These are, of course, merelyexamples and are not intended to be limiting. For example, the formationof a first feature over or on a second feature in the description thatfollows may include embodiments in which the first and second featuresare formed in direct contact, and may also include embodiments in whichadditional features may be formed between the first and second features,such that the first and second features may not be in direct contact. Inaddition, the present disclosure may repeat reference numerals and/orletters in the various examples. This repetition is for the purpose ofsimplicity and clarity and does not in itself dictate a relationshipbetween the various embodiments and/or configurations discussed.

Furthermore, spatially relative terms, such as “beneath,” “below,”“lower,” “above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The apparatus may be otherwise oriented (rotated 90 degreesor at other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly. It should be understoodthat additional operations can be provided before, during, and after themethod, and some of the operations described can be replaced oreliminated for other embodiments of the method.

The advanced lithography process, method, and materials described in thecurrent disclosure can be used in many applications, including fin-typefield effect transistors (FinFETs). For example, the fins may bepatterned to produce a relatively close spacing between features, forwhich the above disclosure is well suited. In addition, spacers used informing fins of FinFETs can be processed according to the abovedisclosure.

FIGS. 1A-1E are cross-sectional views of various stages of a process forforming a photomask, in accordance with some embodiments. FIGS. 1A-1 to1E-1 are top views illustrating the photomask of FIGS. 1A-1E, inaccordance with some embodiments. FIGS. 1A-1E are cross-sectional viewsillustrating the photomask along a sectional line I-I′ in FIGS. 1A-1 to1E-1, in accordance with some embodiments. FIGS. 1A-2 to 1E-2 areperspective views illustrating the photomask of FIGS. 1A-1E, inaccordance with some embodiments.

As shown in FIGS. 1A, 1A-1, and 1A-2, a transparent substrate 110 isprovided, in accordance with some embodiments. The transparent substrate110 has a transmittance ranging from about 85% to about 100%, inaccordance with some embodiments. The transmittance of the transparentsubstrate 110 ranges from about 95% to about 99.9%, in accordance withsome embodiments. The transmittance in the application is measured usinga light which is suitable to be used in an exposure operation of aphotolithography process, in accordance with some embodiments.

The light includes a G-Line with a wavelength of 436 nm, an I-Line witha wavelength of 365 nm, a KrF excimer laser with a wavelength of 248 nm,a DUV excimer laser with a wavelength of 193 nm, or an EUV light with awavelength of about 10 nm to 20 nm, particularly about 13.5 nm±0.3 nm,in accordance with some embodiments. The transparent substrate 110 ismade of fused silica (SiO₂ or fused quartz), calcium fluoride, oranother suitable transparent material.

As shown in FIGS. 1A, 1A-1, and 1A-2, a light blocking layer 120 isformed over the transparent substrate 110, in accordance with someembodiments. The light blocking layer 120 has a transmittance rangingfrom about 0% to about 18%, in accordance with some embodiments. Thetransmittance ranges from about 0% to about 12%, in accordance with someembodiments. The transmittance ranges from about 0% to about 9%, inaccordance with some embodiments. The transmittance ranges from about 0%to about 6%, in accordance with some embodiments.

The light blocking layer 120 is made of an attenuating material or anopaque material, in accordance with some embodiments. The light blockinglayer 120 includes chrome or another material, such as metal (e.g., Au,Mo, or Ti, Ta), metal silicide (e.g., MoSi), metal nitride (e.g., CrN,MoN, TiN, ZrN, TaN, or NbN), metal oxide (e.g., Nb₂O₅, MoO₃, Cr₂O₃,TiO₂, or Ta₂O₅), Si₃N₄, Al₂O₃N, or a combination thereof, in accordancewith some embodiments. The light blocking layer 120 and the transparentsubstrate 110 are made of different materials, in accordance with someembodiments.

In some embodiments, MoSi allows a small percentage of the light to passthrough (typically 6% to 18%). The light blocking layer 120 is formedusing a deposition process, such as a physical vapor deposition processor a chemical vapor deposition process, in accordance with someembodiments.

As shown in FIGS. 1A, 1A-1, and 1A-2, a mask layer 130 is formed overthe light blocking layer 120, in accordance with some embodiments. Themask layer 130 has a main portion 132 and assist portions 134 and 136,in accordance with some embodiments. The assist portions 134 and 136alternately surround the main portion 132, in accordance with someembodiments.

In some embodiments, the main portion 132 has a rectangular shape. Insome embodiments, the assist portion 134 has a bar shape. In someembodiments, the assist portion 136 has a rectangular shape. As shown inFIG. 1A, the main portion 132 is wider than the assist portion 134, inaccordance with some embodiments. As shown in FIGS. 1A-1 and 1A-2, themain portion 132 is wider than the assist portion 136, in accordancewith some embodiments.

The main portion 132 covers a portion 122 a of the light blocking layer120, in accordance with some embodiments. The portion 122 a is over aportion 112 of the transparent substrate 110, in accordance with someembodiments. The assist portions 134 cover portions 124 a of the lightblocking layer 120, in accordance with some embodiments.

The portions 124 a are over portions 114 of the transparent substrate110, in accordance with some embodiments. The assist portions 136 coverportions 126 a of the light blocking layer 120, in accordance with someembodiments. The portion 122 a is wider than the portion 124 a, inaccordance with some embodiments. The portion 122 a is wider than theportion 126 a, in accordance with some embodiments.

The mask layer 130 is made of a material different from that of thelight blocking layer 120, in accordance with some embodiments. In someembodiments, the mask layer 130 is made of a photoresist material. Themask layer 130 is formed using processes including photoresistdeposition, soft baking, mask aligning, exposing (e.g., patterning),baking, developing the photoresist, hard baking, and/or other processes.In some embodiments, the exposing (e.g., patterning) may includeelectron-beam writing, ion-beam writing, mask-less lithography, and/ormolecular imprint.

In some other embodiments, the mask layer 130 is made of anon-photoresist material. The non-photoresist material includes, forexample, a metal material (e.g., Cr). The mask layer 130 is formed usinga photolithography process and an etching process, in accordance withsome embodiments.

As shown in FIGS. 1B, 1B-1, and 1B-2, the light blocking layer 120,which is not covered by the mask layer 130, is removed, in accordancewith some embodiments. The portions 122 a, 124 a, and 126 a remain overthe transparent substrate 110 after the removal process, in accordancewith some embodiments.

The portion 122 a forms a main light blocking structure 122, inaccordance with some embodiments. The portions 124 a and 126 arespectively form assist light blocking structures 124 and 126, inaccordance with some embodiments. The main light blocking structure 122,the assist light blocking structures 124 and 126, and the transparentsubstrate 110 together form a photomask 100, in accordance with someembodiments.

As shown in FIG. 1B, a width W1 of the main light blocking structure 122is greater than a width W2 of the assist light blocking structure 124,in accordance with some embodiments. As shown in FIG. 1B-2, the width W1is greater than a width W3 of the assist light blocking structure 126,in accordance with some embodiments. The width W3 is greater than thewidth W2, in accordance with some embodiments.

The assist light blocking structures 124 and 126 are also referred to assub-resolution assist features, in accordance with some embodiments. Theassist light blocking structures 124 and 126 have small dimensions suchthat the assist light blocking structures 124 and 126 will not imageonto a photoresist layer over a semiconductor substrate (e.g., wafer)when the photomask 100 is irradiated during a subsequent exposureoperation of a photolithography process. The removal process includes anetching process, such as a dry etching process (e.g., a plasma etchingprocess), in accordance with some embodiments.

As shown in FIGS. 1C, 1C-1, and 1C-2, the mask layer 130 is removed, inaccordance with some embodiments. The removal process of the mask layer130 includes an etching process, such as a wet etching process, inaccordance with some embodiments. The removal process of the mask layer130 may also remove the assist light blocking structures 124. Theremoval of the assist light blocking structures 124 may be undesirable.

As shown in FIGS. 1D, 1D-1, and 1D-2, the portions 114 of thetransparent substrate 110 (as shown in FIG. 1A or 1B) are removed toform recesses 114 a in the transparent substrate 110, in accordance withsome embodiments. As shown in FIG. 1D-1, a length L1 of the recess 114 ais substantially equal to a length L2 of the assist portion 134 of themask layer 130 (as shown in FIG. 1A-1) or a length L3 of the assistlight blocking structure 124 (as shown in FIG. 1B-2), in accordance withsome embodiments.

The term “substantially equal to” in the application means “within 10%”,in accordance with some embodiments. For example, the term“substantially equal to” means the difference between the lengths L1 andL2 (or L3) is within 10% of the average between the lengths L1 and L2(or L3), in accordance with some embodiments. The difference may be dueto manufacturing processes.

As shown in FIG. 1D-1, a width W4 of the recess 114 a is substantiallyequal to a width W5 of the assist portion 134 of the mask layer 130 (asshown in FIG. 1A-1) or the width W2 of the assist light blockingstructure 124 (as shown in FIG. 1B-2), in accordance with someembodiments. The term “substantially equal to” means the differencebetween the widths W4 and W5 (or W2) is within 10% of the averagebetween the widths W4 and W5 (or W2), in accordance with someembodiments. The difference may be due to manufacturing processes.

In some embodiments, a depth D1 of the recess 114 a is substantiallyequal to a thickness T1 of the main light blocking structure 122. Theterm “substantially equal to” means the difference between the thicknessT1 and the depth D1 is within 10% of the average between the thicknessT1 and the depth D1, in accordance with some embodiments. The differencemay be due to manufacturing processes.

The portions 114 of the transparent substrate 110 (as shown in FIG. 1Aor 1B) are removed using an etching process, a scratch process, oranother suitable process. The etching process includes an electronbeam-induced etching process, an ion beam-induced etching process, oranother suitable process.

As shown in FIGS. 1E, 1E-1, and 1E-2, assist light blocking structures142 are respectively formed in the recesses 114 a, in accordance withsome embodiments. In this step, a (repaired) photomask 100 a is formed,in accordance with some embodiments. The photomask 100 a includes thetransparent substrate 110, the main light blocking structure 122, andthe assist light blocking structures 124, 126, and 142, in accordancewith some embodiments.

In some embodiments, the recesses 114 a are completely filled with theassist light blocking structures 142. In some embodiments, a top surface142 a of the assist light blocking structure 142 is substantiallyaligned with (or substantially coplanar with) a top surface 116 of thetransparent substrate 110. The term “substantially coplanar” in theapplication may include small deviations from coplanar geometries. Thedeviations may be due to manufacturing processes.

In some embodiments, a thickness T2 of the assist light blockingstructure 142 is substantially equal to the thickness T1 of the mainlight blocking structure 122. The term “substantially equal to” meansthe difference between the thicknesses T1 and T2 is within 10% of theaverage thickness between the assist light blocking structure 142 andthe main light blocking structure 122, in accordance with someembodiments. The difference may be due to manufacturing processes.

The width W4 of the recess 114 a is substantially equal to a width W6 ofthe assist light blocking structure 142, in accordance with someembodiments. The light blocking layer 120 (as shown in FIG. 1A) and theassist light blocking structures 142 are made of different materials, inaccordance with some embodiments. In some other embodiments, the lightblocking layer 120 (as shown in FIG. 1A) and the assist light blockingstructures 142 are made of the same material.

The assist light blocking structures 142 are made of an attenuatingmaterial or an opaque material, in accordance with some embodiments. Theassist light blocking structures 142 are made of chrome or othermaterials, such as metal (e.g., Au, Mo, or Ti, Ta), metal silicide(e.g., MoSi), metal nitride (e.g., CrN, MoN, TiN, ZrN, TaN, or NbN),metal oxide (e.g., Cr₂O₃, Nb₂O₅, MoO₃, TiO₂, or Ta₂O₅), Si₃N₄, Al₂O₃N,or a combination thereof, in accordance with some embodiments. Theassist light blocking structures 142 and the transparent substrate 110are made of different materials, in accordance with some embodiments.

The assist light blocking structures 142 are formed using an electronbeam-induced deposition process, an ion beam-induced deposition process,or another suitable process. In some embodiments, the recesses 114 a andthe assist light blocking structures 142 are formed in the same chamber,such as an electron beam chamber or an ion beam chamber.

Since the assist light blocking structures 142 are formed in therecesses 114 a, the assist light blocking structures 142 are fixed tothe transparent substrate 110 by the recesses 114 a, in accordance withsome embodiments. Therefore, the assist light blocking structures 142are prevented from peeling from the transparent substrate 110, inaccordance with some embodiments. As a result, the formation of therecesses 114 a improves the yield of the process for forming the assistlight blocking structures 142, in accordance with some embodiments.

FIG. 2 is a cross-sectional view of a photomask 100 b, in accordancewith some embodiments. As shown in FIG. 2, the photomask 100 b issimilar to the photomask 100 a of FIG. 1E, except that the recesses 114a of the transparent substrate 110 of the photomask 100 b are partiallyfilled with the assist light blocking structures 142, in accordance withsome embodiments. In some embodiments, a recess R is surrounded by theassist light blocking structure 142 and the transparent substrate 110,in accordance with some embodiments.

FIG. 3 is a cross-sectional view of a photomask 100 c, in accordancewith some embodiments. As shown in FIG. 3, the photomask 100 c issimilar to the photomask 100 a of FIG. 1E, except that the assist lightblocking structures 142 of the photomask 100 c extend out of therecesses 114 a, in accordance with some embodiments. That is, the assistlight blocking structures 142 protrude from the top surface 116 of thetransparent substrate 110, in accordance with some embodiments.

In some embodiments, the thickness T2 of the assist light blockingstructure 142 is substantially equal to the thickness T1 of the mainlight blocking structure 122. In some embodiments, a ratio of the depthD1 of the recesses 114 a to the thickness T1 ranges from about 0.45 toabout 0.55.

FIG. 4 is a cross-sectional view of a photomask 100 d, in accordancewith some embodiments. As shown in FIG. 4, the photomask 100 d issimilar to the photomask 100 c of FIG. 3, except that a ratio of thedepth D1 of the recesses 114 a to the thickness T1 of the main lightblocking structure 122 ranges from about 0.08 to about 0.12.

The top surface 142 a of the assist light blocking structure 142 ispositioned higher than the top surface 122 a of the main light blockingstructure 122 relative to the top surface 116 of the transparentsubstrate 110, in accordance with some embodiments. In some embodiments,the thickness T2 of the assist light blocking structure 142 is greaterthan the thickness T1 of the main light blocking structure 122.

FIG. 5 is a cross-sectional view of a photomask 100 e, in accordancewith some embodiments. As shown in FIG. 5, the photomask 100 e issimilar to the photomask 100 d of FIG. 4, except that the width W4 ofthe recess 114 a of the photomask 100 e is greater than the width W6 ofthe assist light blocking structure 142, in accordance with someembodiments. The sidewalls 142 b of the assist light blocking structures142 are spaced apart from the inner walls 114 b of the recesses 114 a,in accordance with some embodiments.

FIG. 6 is a cross-sectional view of a photomask 100 f, in accordancewith some embodiments. As shown in FIG. 6, the photomask 100 f issimilar to the photomask 100 d of FIG. 4, except that each of the assistlight blocking structures 142 has an upper portion 142 c and a lowerportion 142 d narrower than the upper portion 142 c, in accordance withsome embodiments.

The upper portion 142 c is outside of the recess 114 a, in accordancewith some embodiments. The lower portion 142 d is in the recess 114 a,in accordance with some embodiments. In some embodiments, a width W7 ofthe upper portion 142 c is greater than a width W8 of the lower portion142 d. The width W8 is substantially equal to the width W4 of the recess114 a, in accordance with some embodiments. The width W7 is greater thanthe width W4, in accordance with some embodiments. In some embodiments,a top surface of the main light blocking structure 122 and a top surfaceof the assist light blocking structure 142 are substantially alignedwith or substantially coplanar with each other.

FIG. 7A is a cross-sectional view of a photomask 100 g, in accordancewith some embodiments. FIG. 7B is a top view illustrating the photomask100 g of FIG. 7A, in accordance with some embodiments. FIG. 7A is across-sectional views illustrating the photomask 100 g along a sectionalline I-I′ in FIG. 7B, in accordance with some embodiments.

As shown in FIGS. 7A and 7B, the photomask 100 g is similar to thephotomask 100 f of FIG. 6, except that the transparent substrate 110 ofthe photomask 100 g further has recesses 114 c and 114 d, and the assistlight blocking structure 142 further extends into the recesses 114 c and114 d, in accordance with some embodiments.

The recesses 114 a, 114 c and 114 d are spaced apart from each other, inaccordance with some embodiments. In some embodiments, a distance S1between the recesses 114 a and 114 c is substantially equal to adistance S2 between the recesses 114 c and 114 d. In some otherembodiments, the distance S1 is different from the distance S2.

The length L1 of the recess 114 a, the length L4 of the recess 114 c, orthe length L5 of the recess 114 d is less than the length L2 of theassist portion 134 of the mask layer 130 (as shown in FIG. 1A-1) or thelength L6 of the assist light blocking structures 142, in accordancewith some embodiments.

The length L1 of the recess 114 a, the length L4 of the recess 114 c,and the length L5 of the recess 114 d are different from each other, inaccordance with some embodiments. In some other embodiments, the lengthsL1, L4, and L5 are substantially equal to each other.

The depth D1 of the recess 114 a, the depth D2 of the recess 114 c, andthe depth D3 of the recess 114 d are different from each other, inaccordance with some embodiments. In some other embodiments, the depthsD1, D2, and D3 are substantially equal to each other.

FIGS. 8A-8C are cross-sectional views of various stages of a process forforming a photomask, in accordance with some embodiments. As shown inFIG. 8A, after the step of FIG. 1B, the mask layer 130 is removed, inaccordance with some embodiments. The removal process of the mask layer130 may also remove the assist light blocking structures 124 and themain light blocking structure 122. The removal process of the mask layer130 includes an etching process, such as a wet etching process, inaccordance with some embodiments.

As shown in FIG. 8B, the portions 112 and 114 of the transparentsubstrate 110 (as shown in FIG. 1A) are removed to form recesses 112 aand 114 a in the transparent substrate 110, in accordance with someembodiments. In some embodiments, a width W9 of the recess 112 a issubstantially equal to the width W1 of the main light blocking structure122 (as shown in FIG. 1B).

The portions 112 and 114 of the transparent substrate 110 (as shown inFIG. 1A or 1B) are removed using an etching process, a scratch process,or another suitable process. The etching process includes an electronbeam-induced etching process, an ion beam-induced etching process, oranother suitable process.

As shown in FIG. 8C, a main light blocking structure 144 and assistlight blocking structures 142 are respectively formed in the recesses112 a and 114 a, in accordance with some embodiments. The main lightblocking structure 144 is made of an attenuating material or an opaquematerial, in accordance with some embodiments.

The main light blocking structure 144 is made of chrome or othermaterials, such as metal (e.g., Au, Mo, or Ti, Ta), metal silicide(e.g., MoSi), metal nitride (e.g., CrN, MoN, TiN, ZrN, TaN, or NbN),metal oxide (e.g., Cr₂O₃, Nb₂O₅, MoO₃, TiO₂, or Ta₂O₅), Si₃N₄, Al₂O₃N,or a combination thereof, in accordance with some embodiments. The mainlight blocking structure 144 and the assist light blocking structures142 are made of the same material, in accordance with some embodiments.In this step, a (repaired) photomask 800 is formed, in accordance withsome embodiments.

FIG. 8C-1 is a top view of the photomask 800 of FIG. 8C, in accordancewith some embodiments. FIG. 8C is a cross-sectional views illustratingthe photomask 800 along a sectional line I-I′ in FIG. 8C-1, inaccordance with some embodiments. As shown in FIGS. 8C and 8C-1, thephotomask 800 includes the transparent substrate 110, the assist lightblocking structures 126, 124 and 142, and the main light blockingstructure 144, in accordance with some embodiments.

In some embodiments, the recesses 114 a are completely filled with theassist light blocking structures 142. In some embodiments, a top surface142 a of the assist light blocking structure 142, a top surface 144 a ofthe main light blocking structure 144, and a top surface 116 of thetransparent substrate 110 are substantially aligned with orsubstantially coplanar with each other.

In some embodiments, the thickness T2 of the assist light blockingstructure 142 is substantially equal to the thickness T3 of the mainlight blocking structure 144. The term “substantially equal to” meansthe difference between the thicknesses T2 and T3 is within 10% of theaverage thickness between the assist light blocking structure 142 andthe main light blocking structure 144, in accordance with someembodiments. The difference may be due to manufacturing processes.

FIG. 9 is a cross-sectional view of a photomask 800 a, in accordancewith some embodiments. As shown in FIG. 9, the photomask 800 a issimilar to the photomask 800 of FIG. 8C, except that the assist lightblocking structure 142 and the main light blocking structure 144protrude from the top surface 116 of the transparent substrate 110, inaccordance with some embodiments.

FIG. 10 is a cross-sectional view of a photomask 800 b, in accordancewith some embodiments. As shown in FIG. 10, the photomask 800 b issimilar to the photomask 800 a of FIG. 9, except that main lightblocking structure 144 has extending portions 144 a extending into thetransparent substrate 110, in accordance with some embodiments.

The extending portions 144 a are spaced apart from each other, inaccordance with some embodiments. The extending portions 144 a arespaced apart from each other by the same distance, in accordance withsome embodiments. In some other embodiments, the extending portions 144a are spaced apart from each other by different distances. In someembodiments, the extending portions 144 a are substantially parallel toeach other.

FIG. 10A is a top view of the photomask 800 b of FIG. 10, in accordancewith some embodiments. FIG. 10 is a cross-sectional views illustratingthe photomask 800 b along a sectional line I-I′ in FIG. 10A, inaccordance with some embodiments. As shown in FIGS. 10 and 10A, theextending portions 144 a have a pillar shape, in accordance with someembodiments. The extending portions 144 a are cylindrical pillars, inaccordance with some embodiments.

FIG. 10B is a top view of the photomask 800 b of FIG. 10, in accordancewith some embodiments. FIG. 10 is a cross-sectional views illustratingthe photomask 800 b along a sectional line I-I′ in FIG. 10B, inaccordance with some embodiments. As shown in FIGS. 10 and 10B, theextending portions 144 a have a rectangular shape, in accordance withsome embodiments. The extending portions 144 a have a sheet shape, inaccordance with some embodiments.

FIG. 11 is a cross-sectional view of a photomask 800 c, in accordancewith some embodiments. As shown in FIG. 11, the photomask 800 c issimilar to the photomask 800 b of FIG. 10, except that main lightblocking structure 144 has extending portions 144 a, 144 b, 144 c and144 d extending into the transparent substrate 110, in accordance withsome embodiments.

The extending portions 144 a, 144 b, 144 c and 144 d have differentwidths, in accordance with some embodiments. The extending portions 144a, 144 b, 144 c and 144 d are spaced apart from each other by differentdistances, in accordance with some embodiments.

FIGS. 12A-12D are cross-sectional views of various stages of a processfor forming a semiconductor device structure, in accordance with someembodiments. As shown in FIG. 12A, a substrate 1210 is provided, inaccordance with some embodiments. The substrate 1210 has a surface 1212,in accordance with some embodiments. In some embodiments, the substrate1210 is a bulk semiconductor substrate, such as a semiconductor wafer.For example, the substrate 1210 is a silicon wafer.

The substrate 1210 may include silicon or another elementarysemiconductor material such as germanium. In some other embodiments, thesubstrate 1210 includes a compound semiconductor. The compoundsemiconductor may include silicon germanium, gallium arsenide, siliconcarbide, indium arsenide, indium phosphide, another suitable compoundsemiconductor, or a combination thereof.

In some embodiments, the substrate 1210 includes asemiconductor-on-insulator (SOI) substrate. The SOI substrate may befabricated using a wafer bonding process, a silicon film transferprocess, a separation by implantation of oxygen (SIMOX) process, anotherapplicable method, or a combination thereof.

In some embodiments, various device elements are formed in and/or overthe substrate 1210. The device elements are not shown in figures for thepurpose of simplicity and clarity. Examples of the various deviceelements include transistors, diodes, another suitable element, or acombination thereof.

For example, the transistors may be metal oxide semiconductor fieldeffect transistors (MOSFET), complementary metal oxide semiconductor(CMOS) transistors, bipolar junction transistors (BJT), high-voltagetransistors, high-frequency transistors, p-channel and/or n-channelfield effect transistors (PFETs/NFETs), etc.

Various processes, such as front-end-of-line (FEOL) semiconductorfabrication processes, are performed to form the various deviceelements. The FEOL semiconductor fabrication processes may includedeposition, etching, implantation, photolithography, annealing,planarization, one or more other applicable processes, or a combinationthereof.

In some embodiments, isolation features (not shown) are formed in thesubstrate 1210. The isolation features are used to define active regionsand electrically isolate various device elements formed in and/or overthe substrate 1210 in the active regions. In some embodiments, theisolation features include shallow trench isolation (STI) features,local oxidation of silicon (LOCOS) features, other suitable isolationfeatures, or a combination thereof.

As shown in FIG. 12A, a layer 1220 is formed over the surface 1212 ofthe substrate 1210, in accordance with some embodiments. The layer 1220is a single-layer structure or a multi-layer structure, in accordancewith some embodiments. The layer 1220 is made of an insulating material,in accordance with some embodiments.

The insulating material includes silicon nitride, silicon oxide, siliconoxynitride, a low dielectric constant (low-k) material, an extreme low-k(ELK) material, borosilicate glass (BSG), phosphoric silicate glass(PSG), borophosphosilicate glass (BPSG), fluorinated silicate glass(FSG), a polymer material, one or more other suitable materials, or acombination thereof. The layer 1220 is formed using a chemical vapordeposition process, a spin coating process, or another suitable process.

In some other embodiments, the layer 1220 is made of a conductivematerial. The conductive material includes metal, such as copper,aluminum, tungsten, gold, silver, or a combination thereof, inaccordance with some embodiments. The layer 1220 is formed using aphysical vapor deposition process, a plating process, or anothersuitable process.

As shown in FIG. 12A, a photoresist layer 1230 is formed over the layer1220, in accordance with some embodiments. As shown in FIG. 12A, thephotomask 100 a of FIG. 1E is positioned over the photoresist layer1230, in accordance with some embodiments. The photomask 100 a may bereplaced with the photomask 100 b, 100 c, 100 d, 100 e, 100 f, 100 g,800, 800 a, 800 b, or 800 c of FIG. 2, 3, 4, 5, 6, 7A, 8C, 9, 10, or 11.

As shown in FIG. 12A, an exposure process is performed, in accordancewith some embodiments. During the exposure process, the photomask 100 ais irradiated by a light 1240, in accordance with some embodiments. Thelight 1240 passes through the transparent substrate 110 and irradiates aportion 1230 a of the photoresist layer 1230, in accordance with someembodiments. The photoresist layer 1230 has a portion 1230 b, which isnot irradiated by the light 1240, in accordance with some embodiments.

As shown in FIG. 12B, if the photoresist layer 1230 is made of apositive photoresist, the portion 1230 a is removed, in accordance withsome embodiments. The removal process includes a develop process, inaccordance with some embodiments. The positive photoresist includesphenol-formaldehyde (novolak) resin, epoxy resin, or another suitablematerial.

As shown in FIG. 12C, portions of the layer 1220, which are not coveredby the photoresist layer 1230, are removed, in accordance with someembodiments. The removal process includes an etching process, such as adry etching process, in accordance with some embodiments. As shown inFIG. 12D, the photoresist layer 1230 is removed, in accordance with someembodiments.

FIGS. 13A-13C are cross-sectional views of various stages of a processfor forming a semiconductor device structure, in accordance with someembodiments. As shown in FIG. 13A, after the step of FIG. 12A, if thephotoresist layer 1230 is made of a negative photoresist, the portion1230 b is removed, in accordance with some embodiments. The removalprocess includes a develop process, in accordance with some embodiments.The negative photoresist includes polyisoprene or another suitablematerial.

As shown in FIG. 13B, portions of the layer 1220, which are not coveredby the photoresist layer 1230, are removed, in accordance with someembodiments. The removal process includes an etching process, such as adry etching process, in accordance with some embodiments. As shown inFIG. 13C, the photoresist layer 1230 is removed, in accordance with someembodiments.

FIGS. 14A-14E are cross-sectional views of various stages of a processfor forming a photomask, in accordance with some embodiments. As shownin FIG. 14A, a reflective substrate 1410 is provided, in accordance withsome embodiments. The reflective substrate 1410 has a reflectivityranging from about 50% to about 100%, in accordance with someembodiments. The reflectivity of the reflective substrate 1410 rangesfrom about 65% to about 75%, in accordance with some embodiments.

The reflectivity in the application is measured using a light which issuitable to be used in an exposure operation of a photolithographyprocess, in accordance with some embodiments. The light includes an EUVlight with a wavelength of about 10 nm to 20 nm, particularly about 13.5nm±0.3 nm, in accordance with some embodiments.

The reflective substrate 1410 includes a substrate 1412, a reflectivelayer 1414, and an adhesive layer 1416, in accordance with someembodiments. The substrate 1412 is made of fused silica (SiO₂ or fusedquartz) or another suitable material. The substrate 1412 is opaque to anEUV light, in accordance with some embodiments. The substrate 1412 ismade of doped quartz, which is doped with titanium dioxide, inaccordance with some embodiments. The substrate 1412 has a thickness T4ranging from about 3 mm to about 10 mm, in accordance with someembodiments.

The reflective layer 1414 is formed over the substrate 1412, inaccordance with some embodiments. The reflective layer 1414 is made ofmolybdenum (Mo) and silicon, in accordance with some embodiments. Thereflective layer 1414 has a multilayer structure, in accordance withsome embodiments. The multilayer structure has alternately laminatedmolybdenum films and silicon films, in accordance with some embodiments.

The reflective layer 1414 has a thickness T5 ranging from about 250 nmto about 350 nm, in accordance with some embodiments. The reflectivityof the reflective layer 1414 ranges from about 60% to about 100%, inaccordance with some embodiments. The reflectivity of the reflectivelayer 1414 ranges from about 65% to about 75%, in accordance with someembodiments.

The adhesive layer 1416 is formed over the reflective layer 1414, inaccordance with some embodiments. The adhesive layer 1416 is made ofsilicon, ruthenium, or another suitable material, in accordance withsome embodiments. The adhesive layer 1416 has a thickness T6 rangingfrom about 1 nm to about 6 nm, in accordance with some embodiments. Insome other embodiments, the adhesive layer 1416 is not formed.

As shown in FIG. 14A, a light-absorbing layer 1420 is formed over theadhesive layer 1416, in accordance with some embodiments. Thelight-absorbing layer 1420 is made of a light-absorbing material, suchas tantalum boron nitride (TaBN), tantalum boron oxide (TaBO), tantalumnitride oxide (TaNO), and/or tantalum nitride (TaN), in accordance withsome embodiments. The absorbance of the light-absorbing layer 1420ranges from about 80% to about 100%, in accordance with someembodiments. The absorbance of the light-absorbing layer 1420 rangesfrom about 90% to about 99%, in accordance with some embodiments.

The absorbance in the application is measured using a light which issuitable to be used in an exposure operation of a photolithographyprocess, in accordance with some embodiments. The light includes an EUVlight with a wavelength of about 10 nm to 20 nm, particularly about 13.5nm±0.3 nm, in accordance with some embodiments.

As shown in FIG. 14A, a mask layer 130 is formed over thelight-absorbing layer 1420, in accordance with some embodiments. Themask layer 130 is structurally the same as the mask layer 130 of FIGS.1A and 1A-1, in accordance with some embodiments. The mask layer 130 hasa main portion 132 and assist portions 134 and 136, in accordance withsome embodiments. For the sake of simplicity, FIGS. 14A-14E do not showthe assist portions 136 of the mask layer 130 of FIG. 1A-1, inaccordance with some embodiments.

The main portion 132 covers a portion 1422 a of the light-absorbinglayer 1420, in accordance with some embodiments. The portion 1422 a isover a portion 1410 a of the reflective substrate 1410, in accordancewith some embodiments. The assist portions 134 cover portions 1424 a ofthe light-absorbing layer 1420, in accordance with some embodiments. Theportions 1424 a are over portions 1410 b of the reflective substrate1410, in accordance with some embodiments. The portion 1422 a is widerthan the portion 1424 a, in accordance with some embodiments.

The mask layer 130 is made of a material different from that of thelight-absorbing layer 1420, in accordance with some embodiments. In someembodiments, the mask layer 130 is made of a photoresist material. Themask layer 130 is formed using processes including photoresistdeposition, soft baking, mask aligning, exposing (e.g., patterning),baking, developing the photoresist, hard baking, and/or other processes.In some embodiments, the exposing (e.g., patterning) may includeelectron-beam writing, ion-beam writing, mask-less lithography, and/ormolecular imprint.

In some other embodiments, the mask layer 130 is made of anon-photoresist material. The non-photoresist material includes, forexample, a metal material (e.g., Cr). The mask layer 130 is formed usinga photolithography process and an etching process, in accordance withsome embodiments.

As shown in FIGS. 14A and 14B, the light-absorbing layer 1420, which isnot covered by the mask layer 130, is removed, in accordance with someembodiments. The portions 1422 a and 1424 a remain over the reflectivesubstrate 1410 after the removal process, in accordance with someembodiments. The portion 1422 a forms a main light-absorbing structure1422, in accordance with some embodiments. The portions 1424 arespectively form assist light-absorbing structures 1424, in accordancewith some embodiments. The main light-absorbing structure 1422, theassist light-absorbing structures 1424, and the reflective substrate1410 together form a photomask 1400, in accordance with someembodiments.

As shown in FIG. 14B, a width W11 of the main light-absorbing structure1422 is greater than a width W22 of the assist light-absorbing structure1424, in accordance with some embodiments. The assist light-absorbingstructures 1424 are also referred to as sub-resolution assist features,in accordance with some embodiments.

The assist light-absorbing structures 1424 have small dimensions suchthat the assist light-absorbing structures 1424 will not image onto aphotoresist layer over a semiconductor substrate (e.g., wafer) when thephotomask 1400 is irradiated during a subsequent exposure operation of aphotolithography process. The removal process includes an etchingprocess, such as a dry etching process (e.g., a plasma etching process),in accordance with some embodiments.

As shown in FIG. 14C, the mask layer 130 is removed, in accordance withsome embodiments. The removal process of the mask layer 130 includes anetching process, such as a wet etching process, in accordance with someembodiments. The removal process of the mask layer 130 may also removethe assist light-absorbing structures 1424. The removal of the assistlight-absorbing structures 1424 may be undesirable.

As shown in FIG. 14D, the portions 1410 b of the reflective substrate1410 (as shown in FIG. 14A or 14B) are removed to form recesses 1410 rin the reflective substrate 1410, in accordance with some embodiments.As shown in FIG. 14D, a width W33 of the recess 1410 r is substantiallyequal to the width W22 of the assist light-absorbing structure 1424 (asshown in FIG. 14B), in accordance with some embodiments. The term“substantially equal to” means the difference between the widths W22 andW33 is within 20% of the average between the widths W22 and W33, inaccordance with some embodiments.

In some embodiments, a depth D11 of the recess 1410 r is substantiallyequal to a thickness T11 of the main light-absorbing structure 1422. Theterm “substantially equal to” means the difference between the thicknessT11 and the depth D11 is within 20% of the average between the thicknessT11 and the depth D11, in accordance with some embodiments. Thedifference may be due to manufacturing processes.

The portions 1410 b of the reflective substrate 1410 (as shown in FIG.1A or 1B) are removed using an etching process, a scratch process, oranother suitable process. The etching process includes an electronbeam-induced etching process, an ion beam-induced etching process, oranother suitable process.

As shown in FIG. 14E, assist light-absorbing structures 1432 arerespectively formed in the recesses 1410 r, in accordance with someembodiments. In this step, a (repaired) photomask 1400 a is formed, inaccordance with some embodiments. The photomask 1400 a includes thereflective substrate 1410, the main light-absorbing structure 1422, andthe assist light-absorbing structures 1432, in accordance with someembodiments.

In some embodiments, the recesses 1410 r are completely filled with theassist light-absorbing structures 1432. The recesses 1410 r and theassist light-absorbing structures 1432 pass through the adhesive layer1416 and extend into the reflective layer 1414, in accordance with someembodiments. In some embodiments, a top surface 1432 a of the assistlight-absorbing structure 1432 is substantially aligned with (orsubstantially coplanar with) a top surface 1410 c of the reflectivesubstrate 1410.

In some embodiments, a thickness T22 of the assist light-absorbingstructure 1432 is substantially equal to the thickness T11 of the mainlight-absorbing structure 1422. The term “substantially equal to” meansthe difference between the thicknesses T11 and T22 is within 20% of theaverage thickness between the assist light-absorbing structure 1432 andthe main light-absorbing structure 1422, in accordance with someembodiments. The difference may be due to manufacturing processes.

The width W44 of the assist light-absorbing structure 1432 issubstantially equal to the width W22 of the assist light-absorbingstructure 1424 (as shown in FIG. 14B), in accordance with someembodiments. The light-absorbing layer 1420 (as shown in FIG. 14A) andthe assist light-absorbing structures 1432 are made of differentmaterials, in accordance with some embodiments. In some otherembodiments, the light-absorbing layer 1420 (as shown in FIG. 14A) andthe assist light-absorbing structures 1432 are made of the samematerial.

The assist light-absorbing structures 1432 are made of a light-absorbingmaterial, such as Cr₂O₃, tantalum boron nitride (TaBN), tantalum boronoxide (TaBO), tantalum nitride oxide (TaNO), and/or tantalum nitride(TaN), in accordance with some embodiments. The assist light-absorbingstructures 1432 and the reflective substrate 1410 are made of differentmaterials, in accordance with some embodiments.

The assist light-absorbing structures 1432 are formed using an electronbeam-induced deposition process, an ion beam-induced deposition process,or another suitable process. In some embodiments, the recesses 1410 rand the assist light-absorbing structures 1432 are formed in the samechamber, such as an electron beam chamber or an ion beam chamber.

Since the assist light-absorbing structures 1432 are formed in therecesses 1410 r, the assist light-absorbing structures 1432 are fixed tothe reflective substrate 1410 by the recesses 1410 r, in accordance withsome embodiments. Therefore, the assist light-absorbing structures 1432are prevented from peeling from the reflective substrate 1410, inaccordance with some embodiments. As a result, the formation of therecesses 1410 r improves the yield of the process for forming the assistlight-absorbing structures 1432, in accordance with some embodiments.

FIG. 15 is a cross-sectional view of a photomask 1400 b, in accordancewith some embodiments. As shown in FIG. 15, the photomask 1400 b issimilar to the photomask 1400 a of FIG. 14E, except that the recesses1410 r of the reflective substrate 1410 of the photomask 1400 b arepartially filled with the assist light-absorbing structures 1432, inaccordance with some embodiments. In some embodiments, a recess R1 issurrounded by the assist light-absorbing structures 1432 and thereflective substrate 1410.

FIG. 16 is a cross-sectional view of a photomask 1400 c, in accordancewith some embodiments. As shown in FIG. 16, the photomask 1400 c issimilar to the photomask 1400 a of FIG. 14E, except that the assistlight-absorbing structures 1432 of the photomask 1400 c extend out ofthe recesses 1410 r, in accordance with some embodiments.

That is, the assist light-absorbing structures 1432 protrude from thetop surface 1410 c of the reflective substrate 1410, in accordance withsome embodiments. In some embodiments, the thickness T22 of the assistlight-absorbing structure 1432 is substantially equal to the thicknessT11 of the main light-absorbing structure 1422.

FIG. 17 is a cross-sectional view of a photomask 1400 d, in accordancewith some embodiments. As shown in FIG. 17, the photomask 1400 d issimilar to the photomask 1400 c of FIG. 16, except that the top surface1432 a of the assist light-absorbing structure 1432 is positioned higherthan the top surface 1422 a of the main light-absorbing structure 1422relative to the top surface 1410 c of the reflective substrate 1410, inaccordance with some embodiments. In some embodiments, the thickness T22of the assist light-absorbing structure 1432 is greater than thethickness T11 of the main light-absorbing structure 1422.

FIG. 18 is a cross-sectional view of a photomask 1400 e, in accordancewith some embodiments. As shown in FIG. 18, the photomask 1400 e issimilar to the photomask 1400 c of FIG. 16, except that the assistlight-absorbing structures 1432 does not extend into the reflectivelayer 1414, in accordance with some embodiments. The assistlight-absorbing structures 1432 pass through the adhesive layer 1416, inaccordance with some embodiments. In some other embodiments (not shown),the assist light-absorbing structures 1432 do not pass through theadhesive layer 1416.

FIG. 19 is a cross-sectional view of a photomask 1400 f, in accordancewith some embodiments. As shown in FIG. 19, the photomask 1400 f issimilar to the photomask 1400 b of FIG. 15, except that the assistlight-absorbing structures 1432 of the photomask 1400 f further extendinto the substrate 1412, in accordance with some embodiments. The assistlight-absorbing structures 1432 pass through the reflective layer 1414,in accordance with some embodiments.

FIGS. 20A-20C are cross-sectional views of various stages of a processfor forming a photomask, in accordance with some embodiments. As shownin FIG. 20A, after the step of FIG. 14B, the mask layer 130 is removed,in accordance with some embodiments.

The removal process of the mask layer 130 may also remove the assistlight-absorbing structures 1424 and the main light-absorbing structure1422. The removal process of the mask layer 130 includes an etchingprocess, such as a wet etching process, in accordance with someembodiments.

As shown in FIG. 20B, the portions 1410 a and 1410 b of the reflectivesubstrate 1410 (as shown in FIG. 14A) are removed to form recesses 1411r and 1410 r in the reflective substrate 1410, in accordance with someembodiments. In some embodiments, a width W10 of the recess 1411 r issubstantially equal to the width W11 of the main light-absorbingstructure 1422 (as shown in FIG. 14B).

The portions 1410 a and 1410 b of the reflective substrate 1410 (asshown in FIG. 14A) are removed using an etching process, a scratchprocess, or another suitable process. The etching process includes anelectron beam-induced etching process, an ion beam-induced etchingprocess, or another suitable process.

As shown in FIG. 20C, a main light-absorbing structure 1434 and assistlight-absorbing structures 1432 are respectively formed in the recesses1411 r and 1410 r, in accordance with some embodiments. The mainlight-absorbing structure 1434 and the assist light-absorbing structures1432 pass through the adhesive layer 1416 and extend into the reflectivelayer 1414, in accordance with some embodiments.

The main light-absorbing structure 1434 and the assist light-absorbingstructure 1432 are made of the same material, in accordance with someembodiments. The main light-absorbing structure 1434 and the assistlight-absorbing structure 1432 are made of a light-absorbing material,such as Cr₂O₃, tantalum boron nitride (TaBN), tantalum boron oxide(TaBO), tantalum nitride oxide (TaNO), and/or tantalum nitride (TaN), inaccordance with some embodiments.

The main light-absorbing structure 1434 and the assist light-absorbingstructures 1432 are formed using an electron beam-induced depositionprocess, an ion beam-induced deposition process, or another suitableprocess. In some embodiments, the recesses 1411 r and 1410 r, the mainlight-absorbing structure 1434, and the assist light-absorbingstructures 1432 are formed in the same chamber, such as an electron beamchamber or an ion beam chamber. In this step, a (repaired) photomask2000 is formed, in accordance with some embodiments.

FIG. 21 is a cross-sectional view of a photomask 2000 a, in accordancewith some embodiments. As shown in FIG. 21, the photomask 2000 a issimilar to the photomask 2000 of FIG. 20C, except that the assistlight-absorbing structures 1432 and the main light-absorbing structure1434 protrude from the top surface 1410 c of the reflective substrate1410, in accordance with some embodiments.

FIG. 22 is a cross-sectional view of a photomask 2000 b, in accordancewith some embodiments. As shown in FIG. 22, the photomask 2000 b issimilar to the photomask 2000 a of FIG. 21, except that mainlight-absorbing structure 1434 has extending portions 1434 a extendinginto the reflective substrate 1410, in accordance with some embodiments.

The extending portions 1434 a are spaced apart from each other, inaccordance with some embodiments. The extending portions 1434 a arespaced apart from each other by the same distance, in accordance withsome embodiments. In some other embodiments, the extending portions 1434a are spaced apart from each other by different distances.

In some embodiments, the extending portions 1434 a are substantiallyparallel to each other. In some embodiments, the extending portions 1434a have the same extending length L. In some embodiments (not shown), theextending portions 1434 a have different extending lengths.

FIG. 22A is a top view of the photomask 2000 b of FIG. 22, in accordancewith some embodiments. FIG. 22 is a cross-sectional views illustratingthe photomask 2000 b along a sectional line I-I′ in FIG. 22A, inaccordance with some embodiments. As shown in FIGS. 22 and 22A, theextending portions 1434 a have a pillar shape, in accordance with someembodiments. The extending portions 1434 a are cylindrical pillars, inaccordance with some embodiments.

FIG. 22A shows the remaining assist light-absorbing structures 1424 and1426, in accordance with some embodiments. The remaining assistlight-absorbing structures 1426 are originally covered by the assistportions 136 of the mask layer 130 of FIGS. 14A and 1A-1, in accordancewith some embodiments.

FIG. 22B is a top view of the photomask 2000 b of FIG. 22, in accordancewith some embodiments. FIG. 22 is a cross-sectional views illustratingthe photomask 2000 b along a sectional line I-I′ in FIG. 22B, inaccordance with some embodiments. As shown in FIGS. 22 and 22B, theextending portions 1434 a have a rectangular shape, in accordance withsome embodiments. The extending portions 1434 a have a sheet shape, inaccordance with some embodiments.

FIG. 22C is a cross-sectional views illustrating the photomask 2000 balong a sectional line II-II′ in FIG. 22B, in accordance with someembodiments. As shown in FIGS. 22B and 22C, the assist light-absorbingstructure 1432 has extending portions 1432 b, in accordance with someembodiments. The extending portions 1432 b have different widths or thesame width. The extending portions 1432 b have different extendinglengths or the same extending length. The extending portions 1432 b arespaced apart by different distances or the same distance.

FIG. 23 is a cross-sectional view of a photomask 2000 c, in accordancewith some embodiments. As shown in FIG. 23, the photomask 2000 c issimilar to the photomask 2000 b of FIG. 22, except that mainlight-absorbing structure 1434 has extending portions 1434 a, 1434 b,1434 c and 1434 d extending into the reflective substrate 1410, inaccordance with some embodiments.

The extending portions 1434 a, 1434 b, 1434 c and 1434 d have differentwidths, in accordance with some embodiments. The extending portions 1434a, 1434 b, 1434 c and 1434 d are spaced apart from each other bydifferent distances, in accordance with some embodiments. The extendingportion 1434 b extends into the adhesive layer 1416 and does not extendinto the reflective layer 1414, in accordance with some embodiments.

The extending portion 1434 d passes through the adhesive layer 1416 andthe reflective layer 1414 and extends into the substrate 1412, inaccordance with some embodiments. The extending portions 1434 a, 1434 b,1434 c and 1434 d have different extending lengths L7, L8, L9, and L10,in accordance with some embodiments.

FIG. 24 is a cross-sectional view of a process for forming asemiconductor device structure, in accordance with some embodiments. Asshown in FIG. 24, the substrate 1210, the layer 1220, and thephotoresist layer 1230 of FIG. 12A are provided, in accordance with someembodiments.

As shown in FIG. 24, a photoresist layer 1230 is formed over the layer1220, in accordance with some embodiments. As shown in FIG. 24, thephotomask 2000 of FIG. 20C is positioned over the photoresist layer1230, in accordance with some embodiments. The photomask 2000 may bereplaced with the photomask 1400 a, 1400 b, 1400 c, 1400 d, 1400 e, 1400f, 2000 a, 2000 b, or 2000 c of FIG. 14E, 15-19, or 21-23.

As shown in FIG. 24, an exposure process is performed, in accordancewith some embodiments. During the exposure process, the photomask 2000is irradiated by a light 2410, in accordance with some embodiments. Aportion of the light 2410 is reflected by the reflective substrate 1410and irradiates a portion 1230 a of the photoresist layer 1230, inaccordance with some embodiments.

A portion of the light 2410 is absorbed by the assist light-absorbingstructures 1432 and the main light-absorbing structure 1434, andtherefore a portion 1230 b of the photoresist layer 1230 is notirradiated by the light 2410, in accordance with some embodiments.Thereafter, the steps of FIGS. 12B-12D or the steps of FIGS. 13A-13C areperformed, in accordance with some embodiments.

The photomasks 100 a-100 g, 800, and 800 a-800 c of FIGS. 1E, 2-7B, 8C,and 9-11 are transmissive photomasks, in accordance with someembodiments. The photomasks 1400 a-1400 f, 2000, 2000 a-2000 c of FIGS.14E, 15-19, 20C, and 21-23 are reflective photomasks, in accordance withsome embodiments.

The structures of the assist light-absorbing structures 1432 of thephotomasks 1400 a-1400 f, 2000, 2000 a-2000 c of FIGS. 14E, 15-19, 20C,and 21-23 are similar to or the same as the structures of the assistlight blocking structures 142 of the photomasks 100 a-100 g, 800, and800 a-800 c of FIGS. 1E, 2-7B, 8C, and 9-11, in accordance with someembodiments. The structures of the main light-absorbing structures 1434of FIGS. 20C and 21-23 are similar to or the same as the structures ofthe main light blocking structures 144 of FIGS. 8C and 9-11, inaccordance with some embodiments.

In accordance with some embodiments, photomasks and methods for formingthe same are provided. The methods (for forming the photomask)sequentially form a light blocking layer and a mask layer over atransparent substrate, and remove the light blocking layer, which is notcovered by the mask layer. Thereafter, the methods remove the masklayer. A portion of the light blocking layer originally covered by themask layer is removed during removing the mask layer. The methods form alight blocking structure in the transparent substrate originally underthe portion of the light blocking layer. The formation of the lightblocking structure may repair the damage to the light blocking layercaused by the removal of the mask layer. Furthermore, since the lightblocking structure is formed in the transparent substrate, the lightblocking structure is prevented from peeling from the transparentsubstrate. The methods are able to repair transmissive photomasks. Themethods are also able to repair reflective photomasks.

In accordance with some embodiments, a method for forming a photomask isprovided. The method includes forming a light blocking layer over atransparent substrate. The method includes forming a mask layer over thelight blocking layer. The mask layer covers a first portion of the lightblocking layer, and the first portion is over a second portion of thetransparent substrate. The method includes removing the light blockinglayer, which is not covered by the mask layer. The method includesremoving the mask layer. The first portion of the light blocking layeris removed during removing the mask layer. The method includes removingthe second portion of the transparent substrate to form a first recessin the transparent substrate. The method includes forming a first lightblocking structure in the first recess.

In accordance with some embodiments, a method for forming a photomask isprovided. The method includes forming a light-absorbing layer over areflective substrate. The method includes forming a mask layer over thelight-absorbing layer. The mask layer covers a first portion of thelight-absorbing layer, and the first portion is over a second portion ofthe reflective substrate. The method includes removing thelight-absorbing layer, which is not covered by the mask layer. Themethod includes removing the mask layer. The first portion of thelight-absorbing layer is removed during removing the mask layer. Themethod includes removing the second portion of the reflective substrateto form a recess in the reflective substrate. The method includesforming a light-absorbing structure in the recess.

In accordance with some embodiments, a method for forming a photomask isprovided. The method includes providing a photomask over a photoresistlayer. The photomask includes a transparent substrate having a surface;a first light blocking structure over the surface; and a second lightblocking structure in the transparent substrate. The method includesirradiating the photomask by a light. The light passes through thetransparent substrate and irradiates a first portion of the photoresistlayer.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. A method for forming a photomask, comprising:forming a light blocking layer over a transparent substrate; forming amask layer over the light blocking layer, wherein the mask layer coversthe light blocking layer in a main portion over a first portion of thetransparent substrate and an assist portion over a second portion of thetransparent substrate; removing the light blocking layer, which is notcovered by the mask layer; removing the mask layer, wherein the assistportion of the light blocking layer is removed during removing the masklayer, while the main portion remains; after removing the mask layer andthe assist portion, removing the second portion of the transparentsubstrate to form a first recess in the transparent substrate; andforming a first light blocking structure in the first recess.
 2. Themethod for forming the photomask as claimed in claim 1, wherein a firstlength of the first recess is substantially equal to a second length ofthe mask layer.
 3. The method for forming the photomask as claimed inclaim 1, wherein a first length of the first recess is less than asecond length of the mask layer.
 4. The method for forming the photomaskas claimed in claim 3, wherein the removing of the second portion of thetransparent substrate further forms a second recess in the transparentsubstrate, the second recess is spaced apart from the first recess, andthe first light blocking structure is further formed in the secondrecess and formed over the transparent substrate between the firstrecess and the second recess.
 5. The method for forming the photomask asclaimed in claim 1, wherein the mask layer further covers a thirdportion of the light blocking layer, the third portion is wider than thefirst portion, the third portion is over a fourth portion of thetransparent substrate, the third portion is removed during removing themask layer, the removing of the second portion of the transparentsubstrate further comprises removing the fourth portion to form a secondrecess in the transparent substrate, and the forming of the first lightblocking structure in the first recess further comprises forming asecond light blocking structure in the second recess.
 6. The method forforming the photomask as claimed in claim 1, wherein the mask layerfurther covers a third portion of the light blocking layer, the thirdportion is wider than the first portion, and the third portion isremained after removing the mask layer.
 7. The method for forming thephotomask as claimed in claim 1, wherein the forming of the first recessin the transparent substrate comprises performing an electronbeam-induced etching process or an ion beam-induced etching process, andthe forming of the first light blocking structure comprises performingan electron beam-induced deposition process or an ion beam-induceddeposition process.
 8. The method for forming the photomask as claimedin claim 7, wherein the forming of the first recess and the forming ofthe first light blocking structure are performed in a same chamber. 9.The method for forming the photomask as claimed in claim 1, wherein thelight blocking layer and the first light blocking structure are made ofa same material.
 10. A method for forming a photomask, comprising:forming a light-absorbing layer over a reflective substrate; forming amask layer over the light-absorbing layer, wherein the mask layerdirectly covers the light-absorbing layer in a main portion over a firstportion of the reflective substrate and an assist portion over a secondportion of the reflective substrate; removing the light-absorbing layer,which is not covered by the mask layer; removing the mask layer, whereinthe assist portion of the light-absorbing layer, which is directlycovered by the mask layer, is removed during removing the mask layer,while the main portion remains; removing the second portion of thereflective substrate to form a recess in the reflective substrate; andforming a light-absorbing structure in the recess.
 11. The method forforming the photomask as claimed in claim 10, wherein a first width ofthe light-absorbing structure is substantially equal to a second widthof the first portion of the light-absorbing layer.
 12. The method forforming the photomask as claimed in claim 10, wherein the reflectivesubstrate comprises a substrate and a reflective layer, the reflectivelayer is formed over the substrate, and the recess is formed in thereflective layer.
 13. The method for forming the photomask as claimed inclaim 12, wherein the reflective substrate further comprises an adhesivelayer over the reflective layer, and the recess passes through theadhesive layer.
 14. The method for forming the photomask as claimed inclaim 13, wherein the recess passes through the reflective layer andextends into the substrate.
 15. The method for forming the photomask asclaimed in claim 10, wherein a portion of the light-absorbing structureis outside of the recess.
 16. A photolithography method, comprising:providing a photomask over a photoresist layer, wherein the photomaskcomprises: a transparent substrate having a surface; a main portioncomprising a first light blocking structure over the surface; and anassist portion comprising a second light blocking structure in thetransparent substrate, wherein the second light blocking structure has afirst portion, a second portion, and a third portion, the first portionextends into the transparent substrate to a first depth, the secondportion extends into the transparent substrate to a second depth, thefirst depth is different from the second depth, the first portion andthe second portion are separated from each other by a fourth portion ofthe transparent substrate, and the third portion is over the surface ofthe transparent substrate and is connected to the first portion and thesecond portion; and irradiating the photomask by a light, wherein thelight passes through the transparent substrate and irradiates a firstportion of the photoresist layer.
 17. The photolithography method asclaimed in claim 16, further comprising: removing the first portion ofthe photoresist layer after irradiating the photomask.
 18. Thephotolithography method as claimed in claim 16, further comprising:removing a second portion of the photoresist layer after irradiating thephotomask, wherein the second portion of the photoresist layer is notirradiated by the light.
 19. The photolithography method as claimed inclaim 16, wherein a top surface of the second light blocking structureis aligned with the surface.
 20. The photolithography method as claimedin claim 16, wherein the first portion is wider than the second portion.